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Create Custom Tools

docs/en/learn/create-custom-tools.mdx

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Creating and Utilizing Tools in CrewAI

This guide provides detailed instructions on creating custom tools for the CrewAI framework and how to efficiently manage and utilize these tools, incorporating the latest functionalities such as tool delegation, error handling, and dynamic tool calling. It also highlights the importance of collaboration tools, enabling agents to perform a wide range of actions.

<Tip> **Want to publish your tool for the community?** If you're building a tool that others could benefit from, check out the [Publish Custom Tools](/en/guides/tools/publish-custom-tools) guide to learn how to package and distribute your tool on PyPI. </Tip>

Subclassing BaseTool

To create a personalized tool, inherit from BaseTool and define the necessary attributes, including the args_schema for input validation, and the _run method.

python
from typing import Type
from crewai.tools import BaseTool
from pydantic import BaseModel, Field

class MyToolInput(BaseModel):
    """Input schema for MyCustomTool."""
    argument: str = Field(..., description="Description of the argument.")

class MyCustomTool(BaseTool):
    name: str = "Name of my tool"
    description: str = "What this tool does. It's vital for effective utilization."
    args_schema: Type[BaseModel] = MyToolInput

    def _run(self, argument: str) -> str:
        # Your tool's logic here
        return "Tool's result"

Using the tool Decorator

Alternatively, you can use the tool decorator @tool. This approach allows you to define the tool's attributes and functionality directly within a function, offering a concise and efficient way to create specialized tools tailored to your needs.

python
from crewai.tools import tool

@tool("Tool Name")
def my_simple_tool(question: str) -> str:
    """Tool description for clarity."""
    # Tool logic here
    return "Tool output"

Defining a Cache Function for the Tool

To optimize tool performance with caching, define custom caching strategies using the cache_function attribute.

python
@tool("Tool with Caching")
def cached_tool(argument: str) -> str:
    """Tool functionality description."""
    return "Cacheable result"

def my_cache_strategy(arguments: dict, result: str) -> bool:
    # Define custom caching logic
    return True if some_condition else False

cached_tool.cache_function = my_cache_strategy

Creating Async Tools

CrewAI supports async tools for non-blocking I/O operations. This is useful when your tool needs to make HTTP requests, database queries, or other I/O-bound operations.

Using the @tool Decorator with Async Functions

The simplest way to create an async tool is using the @tool decorator with an async function:

python
import aiohttp
from crewai.tools import tool

@tool("Async Web Fetcher")
async def fetch_webpage(url: str) -> str:
    """Fetch content from a webpage asynchronously."""
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            return await response.text()

Subclassing BaseTool with Async Support

For more control, subclass BaseTool and implement both _run (sync) and _arun (async) methods:

python
import requests
import aiohttp
from crewai.tools import BaseTool
from pydantic import BaseModel, Field

class WebFetcherInput(BaseModel):
    """Input schema for WebFetcher."""
    url: str = Field(..., description="The URL to fetch")

class WebFetcherTool(BaseTool):
    name: str = "Web Fetcher"
    description: str = "Fetches content from a URL"
    args_schema: type[BaseModel] = WebFetcherInput

    def _run(self, url: str) -> str:
        """Synchronous implementation."""
        return requests.get(url).text

    async def _arun(self, url: str) -> str:
        """Asynchronous implementation for non-blocking I/O."""
        async with aiohttp.ClientSession() as session:
            async with session.get(url) as response:
                return await response.text()

By adhering to these guidelines and incorporating new functionalities and collaboration tools into your tool creation and management processes, you can leverage the full capabilities of the CrewAI framework, enhancing both the development experience and the efficiency of your AI agents.